[9.0] Update elasticsearch-keystore.md with special character handling and echo command to enter the password. (#127135)

docs/reference/elasticsearch/command-line-tools/elasticsearch-keystore.md

@@ -88,6 +88,20 @@ Only some settings are designed to be read from the keystore. However, there is
 `-v, --verbose`
 :   Shows verbose output.
 
+## Handling special characters
+
+:::{important}
+Improper handling of special characters can lead to authentication failures and service outages.
+:::
+
+**Exclamation mark**: `!`
+: When using the shell, the combination `\!` is stored as just `!`. This can lead to authentication failures if the password is not stored as intended.
+
+**Quotes**: `"`
+: If quotes are used around the password, they become part of the password itself. This can cause the password to be incorrect when retrieved from the keystore.
+
+**Backslash**: `\`
+: The backslash character needs to be properly escaped. If not escaped correctly, it may be omitted or misinterpreted, leading to incorrect password storage.
 
 ## Examples [elasticsearch-keystore-examples]
 
@@ -150,9 +164,13 @@ To pass the settings values through standard input (stdin), use the `--stdin` fl
 ```sh
 cat /file/containing/setting/value | bin/elasticsearch-keystore add --stdin the.setting.name.to.set
 ```
+Alternatively, you can use the echo command to input the password into the keystore. For example, if the password is `your\!password` :
 
-Values for multiple settings must be separated by carriage returns or newlines.
+```sh
+echo -n 'your\!password' | bin/elasticsearch-keystore add the.setting.name.to.set
+```
 
+Values for multiple settings must be separated by carriage returns or newlines.
 
 ### Add files to the keystore [add-file-to-keystore]